Railway braking apparatus



April 6, 1937- D. F. coBoURN 'v RAILWAY BRAKING APPARATUS Filed May ze, 1936 Tabla/1w @l HIS ATTORNEY Patented pr. 6, 193'? UNITED STATES PATENT OFFICE RAILWAY BRAKING APPARATUS Application May 26,

8 Claims.

My invention relates to railway braking apparatus, and particularly to braking apparatus of the type comprising a braking bar located in the trackway and actuated by a uid pressure motor controlled from a remote point. More particularly, my present invention relates to improvements in braking apparatus of the type described and claimed in Letters Patent of the United States No. 1,888,548, granted to H. L. Bone and J. W. Livingston, on November 22, 1932.

I will describe one form of braking apparatus embodying my invention, and will then point out the novel features thereof in claims.

The accompanying drawing is a view, partly diagrammatic, illustrating one form of railway braking apparatus embodying my invention.

Referring to the drawing, the reference characters I and ia designate the track railsl of a stretch of railway track. Located on opposite sides of rail I, and extending parallel therewith, are two braking bars 2 and 3. Two similar braking bars 2a and 3a extend parallel with rail Ia on opposite sides thereof.

The braking bars 2, 3, 2a, and 32 are operated by a uid pressure motor M, which, in the form here shown, comprises a cylinder 4 containing an auxiliary piston 6 which is movable between the lefthand end of the cylinder and an intermediate point in the cylinder, and a main piston 5 which is movable between a retracted position at the right-hand end of the cylinder and a projected position where it engages the auxiliary piston 6. It will be plain, therefore, that when the auxiliary piston 5 occupies its projected position, in which position it is illustrated in the drawing, the stroke of the main piston 5 is less than when the auxiliary piston 6 occupies its retracted position. The sealing ring of the auxiliary piston 6 is located at 62 in the drawing, and the parts are so proportioned that even when the auxiliary piston occupies its projected position, it does not blank a pipe 28 which communicates with the cylinder e. Piston 5 is provided with flutes or holes by means of which the pipe 28 may at all times communicate with the regions between pistons 5 and 6. The main piston 5 of motor M is attached to a piston rod 1, which piston rod, in turn, is operatively connected with the braking bars 2, 3, 2a, and 3a by means of suitable operating mechanism, one form of which I will now describe.

As here shown, this operating mechanism comprises a link 8 which is connected at one end to the free end of the piston rod l, and at the other end to one arm of a three-arm lever 9 which is pivotally supported in the trackway at I0. The

1936, Serial No. 81,888

second arm of the lever 9 is connected, through a link I I, with a crank I2 whichis pivotally supported in the trackway at I3; and a third arm of lever 9 is connected, through a'link I4, with a crank I5 which is pivotally supported in the trackway at I6. It will be seen, therefore, that the links Il and I4 and the lever 9 constitute a toggle by means of which the cranks I2 and I5r y may be swung in the same directions when the main piston 5 of motor M is operated. The free end of crank I2 is operatively connected with the braking bars 2 and 2a, respectively, by means of resilient connections which include springs Il and I8 and, similarly, the free end of the crank I5 is operatively connected with the braking bars 3 and 32L by means of resilient connections which include springs I9 and 20. It will be seen, therefore, that when piston 5 moves toward the left, the cranks I2 and I5 are both swung in a clockwise direction, so that each braking bar is moved toward the associated rail into a braking position in which it engages the sides of a wheel .of a railway car traversing the rails I and I2. When the piston 5 moves toward the right, however, the cranks I2 and I5 are both swung in a counterclockwise direction, and the braking bars are moved away from the associated rails to their non-braking positions, in which they are out of engagement with the wheels of a passing car. One form of operating mechanism of the type described is disclosed and claimed in Letters Patent oi the United States No. 1,812,191, granted to H. L. Bone, on June 30, 1931, for Railway braking apparatus.

The motor M is controlled by four magnet valves V1, V2, V3, and V4. As here shown, each valve V comprises a valve stem 2|, biased to an upper position by a spring 22, and provided with an armature 23 and a winding 24. When valve Vl is energized, valve stem 2| of this valve moves downwardly against the bias exerted by spring 22,as shown in the drawing, and a pipe 26, which communicates with the left-hand end of cylinder 4, is then connected with a pipe 25 which is constantly supplied with fluid pressure, usually air, from a suitable source not shown in the drawing. When valve AV1 is deenergized, however, valve stem 2I is moved upwardly by spring 22, andpipe 26 is then disconnected from pipe 25. rWhen valve V2 is energized, valve stem 2I of this valve moves downwardly, thereby connecting kpipe 26 with pipe 28, but when valve V2 is deenergized, pipe 26 is disconnected from pipe 28. When valve V3 is energized, a pipe 29 which communicates with the right-hand end of cylinder 4 is vented to atmosphere through a port 21; but when valve V3 is deenergized, pipe 29 is disconnected from atmosphere, and pipe 28 which is disconnected from port 21 when this valve is energized, is then connected with port 21. When valve V4 is energized, valve stem 2l of this valve moves downwardly and connects pipe 29 with pipe 25, but when valve V4 is deenergized,'pipe 29 is disconnected from pipe' 25.

The valves V are controlled in part by a plurality of pressure responsive devices, each designated by the reference character P with a distinguishing exponent. Referring to the pressure responsive device P30, for example, this device comprises a Bourdon tube 44 connected by means of a pipe 3| with pipe 28, and so subjected at all times to the pressure in the middle of cylinder 4. The Bourdon tube 44 controls a contact 45--45a which is closed at all times except when the pressure exceeds a predetermined value which is just suicient to move the braking apparatus to its open position. For example, this pressure might be 30 pounds per square inch. The pressure responsive devices P1040 and P40"50 are similar to the pressure responsive device P30, except that the Bourdon tubes 44 of these devices are connected to a pipe 30 which enters cylinder 4 at such a point that these tubes will be subjected to the pressure in the region between the pistons 5 and 6 until piston 5 has moved toward the left just far enough to move the braking bars to their braking positions, after which these tubes will then be subjected to the pressure in the region between the main piston 5 and the right-hand l end of the cylinder. That is to say, devices P10-20 and F40-50 are responsive to the pressure in front of piston 5 when the piston is in its retracted position, and to the pressure behind the piston when the latter is in its projected position. 40 The pressure responsive devices P10-20 and P40-50 are arranged to operate successively, as the pressure to which these devices are subjected is increased. For example, for all pressures below 10 pounds per square inch, contact 45-450 of each 45 of these devices is closed. If the pressure exceeds l pounds per square inch, however, contact 45-450 of device P1020 opens,` and if the pressure exceeds 20 pounds per square inch, contact 45--45b of device P10-30 closes. In a similar 50 manner, the pressure responsive device P10-50 is adjusted to open its contact 45-45a at 40 pounds per square inch and to close its contact 45-45b at 50 pounds per square inch. The pressure responsive device P10 is likewise similar to the pressure responsive device P30, and is connected to the same pipe 3| to which the device P30 is connected. The contacts 45-45a and 45-4 5b of this latter pressure responsive device are so adjusted, however, that the contact 45-450 will become opened when the 60 pressure in the middle of cylinder 4 exceeds 5 p ounds per square inch, and the contact l5- 45b will become closed. when the pressure in the middle of cylinder 4 exceeds 10 pounds per square inch. It should be pointed out that the specic 65 pressures mentioned for the opening and closing of the contacts of the pressure responsive devices P are given merely by way of illustration, and may be varied as operating conditions require.

The valves V are further controlled by means of a manually operable lever L which, as here shown, is capable of assuming six positions indicated by dotted lines in the drawing, and designated by the reference characters p0, p1, p2, p3, 75 234, and p5. The lever L controls a plurality of contacts 33-34, 35-36, 31--38, 39-40, lil- 42, 4|--43, 46-41, and I6-48. Contacts 4|-42 and 46-41 are closed only when lever L occupies its p0 position; contact 33-34 is closed when lever L occupies its p0 position, its p1 position, or any position intermediate these two positions; contact 35-36 is closed only when lever L occupies it p3 position; contact 31-38 is closed only when lever L occupies its p3 position; contact 39-40 is closed when lever L occupies its p4 position, its p5 position, or any position intermediate these two positions; contact 4l--43 is closed only when lever L occupies its p5 position; and contact 46-48 is closed when lever L occupies its p2 position, its p3 position, its p4 position, or any position intermediate these three positions.

The lever L will usually be located at a point remote from the braking apparatus, as in the control cabin of a classication yard car retarder system, and will be connected with the brakngapparatus by means of line wires extending from the control cabin to the braking apparatus.

As shown in the drawing, lever L occupies its p0 or off position. A circuit is therefore completed for valve V3 at contact 33-34 of lever L, and current flows from a suitable source here shown as a battery B through wires 49 and 50, contact 33-34 of lever L, line wire 5I, an asymmetric unit 52 in its low resistance direction, the winding 24 of valve V3, and common line wire 53 back to battery B. Valve V3 is therefore energized so that the right-hand end of cylinder 4 is connected with atmosphere at port 21. With lever L in its p0 position, a circuit is also completed for valve V2 at contact 4 l-42 of lever L, and current flows from battery B through wire 49, contact lll-42 of lever L, wire 54, line wire 55, an asymmetric unit 56 in its low resistance direction, winding 24 of valve V2, and line wire 53 back to battery B. Valve V2 is therefore also energized, so that pipe 26 is connected with pipe 28. Furthermore, with lever L in its p0 position, if the pressure in the region of cylinder 4 between the pistons 5 and B is below 30 pounds per square inch, a circuit will also be completed for valve V1, which circuit passes from battery B through contact 46-41 of lever L, line wire 51, contact 45-450 of pressure responsive device P30, wire 58, the

winding 24 of valve V1, and wire 53 back to battery B. Valve V1 will therefore become energized and will connect pipe 26 with pipe 25. When pipe 26 becomes connected with pipe 25 under these conditions, iiuid pressure will be admitted to the left-hand end of cylinder 4, and also to the region between the pistons 5 and 6, until the pressure in these regions exceeds 30 pounds per square inch, at which time contact 45-45a of pressure responsive device P30 will open and will deenergize valve V1. All circuits for valve V4 are open and this valve is therefore deenergized. .It will be seen, therefore, that when lever L occupies its p0 position, piston 5 of motor M is held in its extreme right-hand position in cylinder 4 by a pressure of 30 pounds per square inch, and the braking bars therefore occupy their retracted or ineffective positions. Since the piston 5 occupies its extreme right-hand position, the Bourdon tubes 44 of the pressure responsive devices P10-20 and P-5o are subjected to the pressure in the region of cylinder 4 between the pistons 5 and 6. Contact --45b of device P10-30 and contact 45--45a of device F40-50 are therefore both closed, while contact 45-45a of pressure respon/sive device P10-20 and contact 45-450 of device F40-50 are therefore open. Furthermore, since pipe 28 is constantly subjected to the pressure in the region of cylinder 4 between the pistons 5 and 6, and since the pressure in this region is main- 5 tained at 30 pounds per square inch under these conditions, contact 45-45a of pressure responsive device P5-10 is open and contact 45--45l0 of this device is closed.

In explaining the operation of the apparatus as a whole, I will rst assume that the operator wishes to make a comparatively light brake application. To do this, he will move lever L from its p0 to its p2 position. This movement of lever L will open contacts 33-34 and 4l-42 of the l5 lever, and will thus interrupt the circuits which were previously closed for valves V3 and V2, so that these valves will both become deenergized. The deenergization of valve V3 will disconnect pipe 29 from port 21 and will connect pipe 28 with port 21, thereby preventing the escape of uid from the region of cylinder 4 on the right-hand side of piston 5, and permitting uid to escape from the region of cylinder 4 between the pistons 5 and 6; while the deenergization of valve V2 will disconnect pipe 26 from pipe 28, thus preventing the fluid which was previously supplied to cylinder 4, to hold auxiliary piston 6 in its projected position, from escaping through port 21. The movement of lever L to its p2 position also opens contact 46--41 of the lever and closes contacts 35-36 and 46-48. When contact 46-41 becomes opened, it interrupts the previously traced circuit for valve V1, and if the circuit for this valve is not already open at contact l5-45a of pressure responsive device P30, as will be the case if the pressure of the fluid in the region of cylinder 4 between the pistons 5 and 6 at the instant lever L is moved to its p2 position is above 30 pounds per square inch, valve Vl will become 40 deenergized and will cut 01T the supply of fluid to the left-hand end of cylinder 4. If, however, valve V1 is already deenergized, the opening of contact 46-41 of lever L will, of course, have no effect on valve V1. Valve V1, however, will not 4-5 long remain deenergized under these conditions because when contact 46--48 of lever L and contact 45--458v of pressure responsive device P30,are both closed, another circuit is completed for valve V1, which circuit is similar to the previously traced 50 circuit for this valve with the exception that this other circuit includes contact 46-48 of lever L in place of contact 46-41; and, if contact 45-45a of pressure responsive device P30 is not closed when contact 46-48 becomes closed, the pressure in the region of cylinder 4 between pistons 5 and 6 will soon decrease suiiciently to permit this contact to become closed. The energization of valve V1 will, of course, cause fluid rat full line pressure to be admitted to the left-hand end of 00 cylinder 4, which uid will hold auxiliary piston 6 in its projected position in which it is shown in the drawing. When contact 35-36 of lever L becomes closed, the pressure of the uid in the region of cylinder 4 between the pistons 5 and 6 G5 will still be sufciently high, so that contact 45-45b of pressure responsive device P10-20 and contact 45-4 5D of pressure responsive device PF1-10 will both be closed, and, as a result, the closing of contact 3536 will complete a circuit for valve V4, which circuit may be traced from a battery C through line wire 53, winding 24 of valve V4, Wire 60, an asymmetric unit 6| in its low resistance direction, contact 45--45b of pressure responsive device P540, wire 62, contact 45--45b of f5 pressure responsive device P10-20, Wire 63, line wire 5I, contact 35i-36 of lever L, and wires 64 and 65 back to battery C. Valve V4 will therefore become energized and will connect pipe 29 with pipe 25, thus causing fluid at full line pressure to be supplied to the right-hand end of cylinder 4. This pressure will drive piston 5 toward the left, thereby moving the braking bars toward their braking positions. When piston 5 has been moved toward the left to the position in which the braking bars will just engage the wheels of a car passing through the braking apparatus, Bourdon tubes 44 of the pressure responsive devices P10r20 and F40-50 will become subjected to the pressure in the right-hand end of the cylinder, and due to the fact that full line pressure is admitted to cylinder 4 to move the braking bars toward their braking positions, the piston 5 will probably reach this position before the pressure of the fluid in the region of cylinder 4 between the pistons 5 and 6 has decreased to the pressure at which the contact 45-45b of either one of the pressure responsive devices P10-20 or P540 becomes opened. It follows, therefore, that while the braking bars are being moved to their braking positions, the circuit for valve V4 will probably remain closed. However, if the uid in the region of cylinder'4 between the pistons 5 and 6 shouldbecome vented to atmosphere at a sufficiently rapid rate to permit the contact 45-45b of either of the pressure responsive devices P10-20 or P510 to open and deenergize valve V4 before the braking bars reach their full braking positions, thus causing the supply of fluid pressure to the right-hand end of cylinder 4 to become cut off, the expansion of the fluid previously supplied to this end of the cylinder will complete the movement of the braking bars. When the piston 5 reaches the position in which the Bourdon tubes 44 of the pressure responsive devices P10-20 and F40-50 become subjected to the pressure of the fluid in the right-hand end of cylinder 4, if contact 45---45b of device P10-20 has become opened, this contact will immediately be'- come closed, and if the contact is still closed, it will remain closed at least temporarily. Furthermore, Contact 45-45a of pressure responsive device P10-50 will become open, and contact 45--45lo of device F40-50 will become closed. The operation of the contacts 45-45a and 45---45l0 of the pressure responsive device F40-50 under these conditions, however, will have no effect on the remainder of the apparatus. As soon as the pressure in the region of cylinder 4 between the pistons 5 and 6 has decreased to the pressure at which contact 45-450 of pressure responsive dee vice P5-10 becomes opened, if valve V4 has not already become deenergized, this valve will become deenergized and will cut off the supply of fluid pressure to the right-hand end of cylinder 4, and when the pressure in the region of cylinder 4 between the pistons 5 and 5 has decreased to,

the pressure at which contact 45-45a of pressure responsive device P5-10 becomes closed, a circuit will become completed for valve V3 passing from battery C through wire 53, the winding 24 of valve V3, wire 56, contact 45---45a of pressure responsive device P510, wire 62, contact 45-45b of pressure responsive device P10-20, wire 63, line wire` 5I, contact 35-36 of lever L, and wires'64 and 65 back to battery C. Valve V3 will therefore become energized, and will vent iluid from the right-hand end of cylinder 4 until the pressure of the fluid in this end of the cylinder decreases to 20 pounds per square inch, at which time contact 45-45D of pressure responsive device P10-20 will open and will deenergize valve V3, thus preventing the further escape of fluid from the right-hand end of cylinder 4. If the pressure in the right-hand end of cylinder 4' decreases below 10 pounds per square inch for any reason,

contact 45--45a of pressure responsive device P10-20 will become closed and will complete another circuit for valve V4 passing `from battery C through line wire 53, winding 24 of valve V4, wire 6U, asymmetric unit 6l inv its low resistance direction, wire 61, contact 45-454 of pressure responsive device P10-20, ywire 63, line wire 5I, contact 35-36 of leverL, and wires 64 and 65 back to battery C. Valve V4 will therefore again 5 become energized, and will again admit iluid.

pressure to the right-hand end of vcylinder 4 until the pressure builds up to a pressure of pounds per square inch, at which time contact 45--45EL of device P10-20 will open and will deenergize valve V4.

It will be apparent, of course, that as soon as the pressure of the fluid in the right-hand end of cylinder 4 decreases below 50 pounds per square inch, contact 45-45b of device F40-5 will open, and that as soon as the pressure in the right-hand end of cylinder 4 decreases below 40 pounds per square inch, contact 45---45a of pressure responsive device F40-5 will become' closed. The operation of the contacts 45--45a and 45-45b of pressure responsive device P40-50 under these condi- 0tions, however, will have no effect on the remainder of the apparatus. It will be seen, therefore, that when lever L occupies its p2 position, piston 5 is urged toward the left by a pressure of between 10 and 20 pounds per square inch. The movement of piston 5 toward the left under these conditions is limited by the auxiliary piston B, which as pointed out hereinbefore, is held in its projected position by fluid at full line pressure, and the parts are so proportioned that the movement of lever 9 caused by this movement of piston 5 does not bring the (toggle of which lever 9 forms a part, to its dead center position. It follows, therefore, that when a car enters the braking apparatus, the brakings bars may be forced away from the rails, thereby transmitting the reaction of the wheels through the operating mechanism to the piston 5. As a result, the piston 5 may be moved slightly toward the right, thereby cushioning the braking action of the braking n apparatus against the volume of air in cylinder 4.

If the operator desires to make a more powerful brake application, he will move lever L to its p3 position. If, when he does this, the lever previously occupied its p0 position in which it is shown in the drawing, the operation of the apparatus will then be similar to that just described with the following exceptions. Valve V4 will now initially become energized over a circuit which passes from battery C through line wire 53, winding 24 of valve V4, wire 60, asymmetric unit 6l in its low resistance direction, wire 61, contact 45--45a of pressure responsive device P4040, wire E8, an asymmetric unit 69 in its low resistance direction, line wire 55, contact 31-38 of lever L, and wires 64 and 65 back to battery C. When piston 5 has moved toward the left to the position in which the pressure responsive devices P19-,2 and F40-50 become subjected to the pressure of the fluid in the right-hand end of cylinder -4, con- 0 tact l5-452L of pressure responsive device F40-5 will open and contact 45-45b of this pressure responsive device will become closedfV The opening of contact 45--45a of pressure responsive device P459 will interrupt the' circuit which' was previously closed for valve V4, and 'ifcontact' icm/ici 45---45b of pressure responsive device P51U is then closed, another circuit for valve V4 will be-v come completed which circuit may be traced from battery C through line Wire- 53, Winding 24 of valve V4, wire 60, asymmetric unit 6I in its low resistance direction, contact 45--45b of pressure responsive device P5-10, Contact 45--45b of pressure responsive device P40-50, wire 68,' asymmetric unit 69 in its low resistance direction, line Wire 55, contact 31-38 of lever L, and Wires 64 and 65 back to battery C. If, however, contact 45--45a of pressure responsive device P51 is closed when contact 45`45b of pressure responsive device F40-50 becomes opened,v all circuits for valve V4 will then be open, and a circuit for valve V3 Will become closed which latter circuit may be traced from battery C through line wire 53, the winding 24 of valve V3, wire 56, contact 45--45a of pressure responsive device P540, contact 45--45D of pressure responsive device P4U-50, wire 68, asymmetric unit 69 in its low resistance direction, line wire 55, contact 31--38 of lever L, and wires 64 and 65 to battery C. Valve V4 will therefore become deenergized and will cut off the supply of uid pressure to the right-hand end of cylinder 4, and valve V3 will become energized and will vent fluid from the right-hand end of cylinder 4. The valve V3 will continue to vent fluid from the righthand end of cylinder 4 until the pressure of the fluid in this end of the cylinder decreases to 50 pounds per square inch, at which time contact 4.5--45b of pressure responsive device P4C-50 will open and will deenergize this valve. If the pressure in the right-hand end of cylinder 4 now decreases below 40 pounds per square inch, contact 45---451L of pressure responsive device wF40-50 will again become closed and will complete the previously traced circuit for valve V4. Valve V4 will therefore again become energized and will admit iiuid pressure to the right-hand end of cylinder 4 until the pressure increases to 40 pounds per square inch at which time contact 45--45 of pressure responsive device F40-5 will open and willl deenergize valve V4. It will be apparent, therefore, that when lever L occupies its p3 position, thepiston 5 is forced toward the left-hand end of cylinder 4, and is held against auxiliary piston 6, by a fluid at a pressure of between 40 and 50 pounds per square inch.

If, when lever L is moved to its p3 position to increase the braking force, the lever had prevously occupied its p2 position, piston 5 will already be moved to the left to the position in which the Bourdon tubes 44 of the pressure responsive devices P120 and F40-50 are subjected to the pressure of the fluid in the right-hand end of cylinder 4, and the fluid in the region of cylinder 4 between pistons 5 and G will alreadyvbe at atmospheric pressure so that contact 45-454v of device ,P4-1 will be closed and contact l5-45b of this device willbe open. As a result, valvey V4 will initially become' energized overthe same circuit as when'v lever L is moved to its p3 position from its p9 position, but as soon as the pressure in the righthand end of cylinder 4 has increased to 40 pounds per square inch, this valve will immediately become deenergized. After this valve once becomes deenergized, the valves V4 and V3 will then operate to maintain the fluid in the right-hand end of cylinder 4 at a pressure of between 40 and 50 pounds per square inch in a manner which will be readily understood froman inspection of the drawing, and fromV the foregoing description, without further detailed description.

If the operator moves4 lever L to-its p4 position,

, V1 including contact 46-43 of lever L, so that the movement of piston 5 toward the left will be arrested when it engages the auxiliary piston 6. The circuit over which valve V4 becomes energized under these conditions remainsl continuously closed, and it Will be apparent, therefore, that piston 5 will now be held in the position in which it engages the auxiliary piston 6 by fluid at full line pressure.

If it is desirable to apply a still higher braking force, the operator will move lever L to its p5 position, thereby opening contact 46-48 of lever L and closing contact 4I-43 of lever L. When contact 46-48 becomes opened, the circuit previously traced for valve V1 including this contact becomes interrupted and valve V1 therefore becomes deenergized, so that the supply of fluid pressure to the left-hand end of cylinder 4 is cut oi. When contact 4I-43 of lever L becomes closed, a circuit is completed for valve V2 which is similar to the circuit previously traced for this valve except that this latter circuit includes contact 4|-43 of lever L in place of contact 4I--42 of lever L. Valve V2 therefore becomes energized, and since all circuits for valve V3 are now open, so that valve V3 is deenergized, the left-hand end of cylinder 4 is vented to atmosphere. Furthermore, since contact 39-40 of lever L is closed under these conditions, the previously traced circuit for valve V4 including this contact isl closed,`

and valve V4 is therefore also energized. Fluid.' at full line pressure is therefore admitted to the right-hand end of cylinder 4 in the manner previously described, and since the left-hand end of cylinder 4 is now vented to atmosphere, this pressure moves the pistons 5 and 5 to the extreme left-hand end o the cylinder. It will be apparent, therefore, that under these conditions, piston 5 will be held in its eXtreme left-hand position by fluid at full line pressure. The parts are so proportioned that when piston 5 occupies this position, lever 9 occupies the position in which the toggle of which it forms a part is nearly on dead center. 'When the parts occupy these positions, the reaction of ordinary car wheels is not sufficient to move the toggle mechanism, and the entire forces exerted by the springs I1, I8, I9, and 2D of the resilient connections are available to hold the braking bars against the wheels of the car.

It should be observed that if the operator moves lever L from a position corresponding to a higher braking force to a position corresponding to a lower braking force, the apparatus will immedi.- ately and automatically reduce the braking force to a value corresponding to the new position of the lever for reasons which will be apparent from the drawing without tracing the operation in detail.

In order to restore the apparatus from its closed or eiective position to its open or ineffective position, the operator moves lever L to its p0 position in which it is illustrated in the drawing.` The closing of contacts 33-34, lll- 42, and 46--41 of lever L under these conditions completes the circuits previously traced for valves V1, V2, and V3, and these valves therefore all now become energized. rllhe energization of valve V1 admits fluid pressure to the left-hand end of cylinder 4 so that the auxiliary piston 6 is moved' to its projected position in which it is illustrated in the drawing. The energization of valve V2 connects pipe 2t with pipe 28, and since valve V1 is energized so that pipe 26 is supplied with fluid pressure, fluid pressure is then admitted to the region between the pistons 5 and 6. The energization of Valve V3 disconnects pipe 28 from atmosphere and connects pipe 29 with atmosphere. When pipe 29 becomes connected with atmosphere, the pressure in the right-hand end of cylinder 4 becomes eX- hausted, and the pressure between the pistons 5 and 6 therefore moves piston 5 toward the right to restore the braking apparatus to its `open or ineffective position in which it is illustrated in the drawing. If the pressure in the region of cylinder 4 between the pistons 5 and 5 exceeds 30 pounds per square inch during the movement of piston 5 toward the right, contact 45-450 of pressure responsive device P30 will open as previously described, and will interrupt the circuit for valve V1 including this contact. Valve V1 will, therefore, become deenergized, and will cut off the supply of iiuid pressure to the region of cylinder 4 between the auxiliary piston and the adjacent end of the cylinder and between the pistons 5 and 6. When the pressure has again dropped below 30 pounds per square inch, contact 45-45a of pressure responsive device P30 will again become closed to restore the circuit for valve V1. Itwill be seen, therefore, that piston 5 is moved to its right-hand position, and is subsequently maintained in this position, by a pressure of 30 pounds per square inch. This pressure will cause contact l5-l5b of pressure responsive device P1020 to become closed, and will also cause contact 45-450 of pressure responsive device P5-10 to become closed. When the piston 5 reaches its right-hand position, the parts will all be restored to their normal conditions in which they are shown in the drawing.

If, after the parts have been restored to their normal positions in which they are shown inthe drawing, it is not desired to immediately use the retarder, the operator will then move lever L to its p1 or exhaus position. This movement of the lever will interrupt the circuits which were previously closed for the valves V1 and V2, thus causing these valves to become deenergized. The circuit for valve V3, however, will remain closed and this valve will therefore remain energized. With valves V1 and V2 deenergized and valve V3 energized, the supply of fluid pressure to the region of cylinder 4 between the auxiliary piston 6 and the left-hand end of the cylinder and between the pistons 5 and 6 will become cut off, and the iiuid which was previously supplied to' these regions of the cylinder will become trapped in the cylinder, thus causing the braking bars to be held in their non-braking positions. It should be noted, however, that since the valves V1 and V2 are both deenergized, the amount of electrical energy consumed by the braking apparatus under these conditions will be considerably less than if the lever were allowed to remain in its p0 or off position.

It should be pointed out that the functions of the rectiers 52, 5'5, 6I, and 69 is to permit certain ones of the line wires to be used in more than one circuit without causing improper energization of the valves V, whereby the number of line wires required to effect the desired operating functions is reduced to a minimum.

Although I have herein ushown and described only one form of railway braking apparatus embodying my invention, it is understood that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, means. for at times admitting fluid pressure to said cylinder in front of said piston to move it to its retracted position, two magnet valves, means controlled by the one valve for admitting fluid pressure behind said piston to move it to its projected position, means controlled by the other valve for exhausting fluid pressure from behind said piston, pressure responsive means connected with said cylinder at such point as to be subjected to the pressure behind said piston when and only when said piston has been moved away from its retracted position more than a predetermined distance, other fluid pressure responsive means connected with said cylinder at such point as to be constantly subjected to the pressure in front of said piston, means controlled by said two pressure responsive means for selectively controlling said two valves, and car retarding means operated by said piston.

2. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, means for at times admitting uid pressure to said cylinder in front of said piston to move it to its retracted position, two magnet valves, means controlled by the one valve for admitting fluid pressure behind said piston to move it to its projected position, means controlled by the other valve for exhausting fluid pressure from behind said piston, pressure responsive means connected with said cylinder at such point as to be subjected to the pressure behind said piston when and only when said piston has been moved away from its retracted position more than a predetermined distance, other fluid pressure responsive means connected with said cylinder at such point as to be constantly subjected to the pressure in front of said piston, a manually operable lever movable to different positions, means controlled by said lever and by said two pressure responsive means for selectively controlling said two valves, and car retarding means operated by said piston.

3. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, means for at times admitting fluid to said cylinder in front of said piston to move it to its retracted position, a first magnet valve effective when energized for admitting fluid behind said piston to move it to its projected position, a second magnet valve effective for exhausting uid from behind or in front of said piston according as said valve is energized or deenergized, a rst iiuid pressure responsive device constantly subjected to the pressure of the fluid in front of said piston and a second fluid pressure responsive device at times subjected to the pressure of the iiuid in front of said piston and at other times to the pressure behind said piston depending upon the position of said piston, means controlled by said two uid 75 pressure responsive devices for selectively controlling said valves, and car retarding means operated by said piston.

4. Railway braking apparatus comprising a cylinder, apiston movable therein having a retracted and a projected position, means for at times admitting uid to said cylinder in front of said piston to move it to its retracted position, a first magnet valve effective when energized for admitting uid behind said piston to move it to its projected position, a second magnet valve effective for exhausting uid from behind or in front of said piston according as said Valve is energized or deenergized, a first fluid pressure responsive device constantly subjected to the pressure of the fluid in front of said piston and a second fluid pressure responsive device at times subjected to the pressure of the fluid in front of said piston and at other times to the pressure behind said piston depending upon the position of said piston, a manually operable lever, means controlled by said lever and by said two fluid pressure responsive devices for selectively controlling said valves, and car retarding means operated by said piston.

5. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, a rst magnet valve for controlling the admission of iiuid pressure to said cylinder on one side of said piston, a second magnet valve for controlling the admission of fluid to said cylinder on the other side of said piston, a third magnet valve for controlling the exhaust of iiuid from said cylinder on both sides of said piston, a first iiuid pressure responsive device constantly subjected to the pressure of the uid in said cylinder on one side of said piston, a second fluid pressure responsive device connected with said cylinder at such point that said second device will at times be subjected to the pressure of the fluid on one side of said piston and at other times to the pressure of the uid on the other side of said piston, a manually operable lever, means controlled by said lever for controlling said first valve, means controlled jointly by said lever and by said two pressure responsive devices for selectively controlling said second and third valves, and car retarding means controlled by said piston.

6. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, a rst magnet valve effective when energized for admitting iiuid pressure in front of said piston to move it to its retracted position, a second magnet valve effective when energized for admitting fluid pressure behind said piston to move it to its projected position, a third magnet valve for exhausting fluid pressure from in front of said piston or behind said piston according as said third valve is deenergized or energized, a first pressure responsive device connected with said cylinder at such point as to be subjected to the pressure in front of said piston when the piston is in its retracted position and to the pressure behind said piston when the piston has been moved away from its retracted position more than a predetermined distance, a second pressure responsive device connected with said cylinder at such point as to be constantly subjected to the pressure in front of said piston, contacts controlled by said pressure responsive devices, a manually operable lever, means controlled by said lever for at times energizing said first magnet valve, other means controlled by said lever and by said contacts for selectively energizing said second and third magnet valves, and car retarding means operated by said piston.

7. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, a first magnet valve effective when energized for admitting fluid pressure in front of said piston to move it to its retracted position, a second magnet valve effective when energized for admitting fluid pressure behind said piston to move it to its projected position, a third magnet valve for exhausting fluid pressure from in front of said piston or behind said piston according as said third valve is deenergized or energized, a rst pressure responsive device connected with said cylinder at such point as to be subjected to the pressure in front of said piston when the piston is in its retracted position and to the pressure behind said piston when the piston has been moved away from its retracted position more than a predetermined distance, a second pressure responsive device connected with said cylinder at such point as to be constantly subjected to the pressure in front of said piston, a first and a second contact controlled by said first uid pressure responsive device in such manner that said rst contact will be closed when and only when the pressure to which said rst device is subjected is below a predetermined pressure and that said second contact will be closed when and only when the pressure to which said rst device is subjected is above a predetermined pressure which is higher than the pressure at which said first contact becomes closed, a third and a fourth contact controlled by said second fluid pressure responsive device in such manner that said third contact will be closed when and only when the pressure to which said second device is subjected is below a predetermined pressure which is less than the pressure at which said first contact becomes closed and that said fourth contact will be closed when and only when the pressure to which said second device is subjected is above a predetermined pressure which is equal to or less than the pressure at which said rst contact becomes closed, a manually operable lever provided with a fth and a sixth contact which are closed in one position of the lever and with a seventh contact which is closed in another position of the lever, an energizing circuit for said first valve including the fifth contact, a rst circuit for said second valve including said second, fourth, and seventh contacts, a second circuit for said second valve including said first and seventh contacts, a rst circuit for said third valve including said sixth contact, a second circuit for said third valve including said second, third, and seventh contacts, and car retarding means controlled by said piston.

8. Railway braking apparatus comprising a cylinder, a piston movable therein having a retracted and a projected position, means for at times admitting uid to said cylinder in front of said piston to move it to its projected position, a first magnet valve effective when energized for admitting fluid behind said piston to move it to its projected position, a second magnet valve effective for exhausting fluid from behind or in front of said piston according as said valve is energized or deenergized, a iirst fluid pressure responsive device connected with said cylinder at such point as to be subjected to the pressure in front of said piston when the piston is in its retracted position and to the pressure behind said piston when the piston has been moved away from its retracted position more than a predetermined distance, a second pressure responsive device connected with said cylinder at such point as to be constantly subjected to the pressure in front of said piston, a first and a second contact controlled by said first iluid pressure responsive device in such manner that said rst contact will be closed when and only when the pressure to which said rst device is subjected is below a predetermined pressure and that said second Contact will be closed when and only when the pressure to which said rst device is subjected is above a predetermined pressure which is higher than the pressure at which said first contact becornes closed, a third and a fourth contact controlled by said second fluid pressure responsive device in such manner that said third contact will be closed when and only when the pressure to which said second device is subjected is below a predetermined pressure which is less than the pressure at which said first contact becomes closed and that said fourth contact will be closed when and only when the pressure to which said second device is subjected is above a predetermined pressure which is equal to or less than the pressure at which said iirst contact becomes closed, a first circuit for said rst valve including said first contact, a second circuit for said rst valve including said second and fourth contacts, a circuit for said second valve including said second and third contacts, and car retarding means controlled by said piston.

DELBERT F. COBO'URN. 

